High-Density Isolated FeO Sites on a Single-Crystal CuO(100) Surface.

Single-atom catalysts have recently been subject to considerable attention within applied catalysis. However, complications in the preparation of well-defined single-atom model systems have hampered efforts to determine the reaction mechanisms underpinning the reported activity. By means of an atomic layer deposition method utilizing the steric hindrance of the ligands, isolated FeO motifs were grown on a single-crystal CuO(100) surface at densities up to 0.21 sites per surface unit cell. Ambient pressure X-ray photoelectron spectroscopy shows a strong metal-support interaction with Fe in a chemical state close to 3+. Results from scanning tunneling microscopy and density functional calculations demonstrate that isolated FeO is exclusively formed and occupies a single site per surface unit cell, coordinating to two oxygen atoms from the CuO lattice and another through abstraction from O. The isolated FeO motif is active for CO oxidation at 473 K. The growth method holds promise for extension to other catalytic systems.